1. Field of the Invention
The present invention relates to a zinc oxide precursor in use for deposition of a zinc oxide-based thin film and a method of depositing a zinc oxide-based thin film using the same.
2. Description of Related Art
Flat panel displays, such as a thin-film transistor liquid crystal display (TFT-LCD), a plasma display panel (PDP), a field emission display (FED), and an organic light-emitting diode (OLED), photovoltaic cells using photoelectric effect, touch screens, or the like require a transparent conducting electrode, i.e. a conductive material which does not block light.
The key material for the transparent conducting electrode is tin (Sn)-doped indium oxide (In2O3), i.e. indium tin oxide (ITO). ITO is popular as a transparent electrode material since it has superior electric conductivity owing to its low specific resistivity of about 1 or 2×10−4 Ωm, has high transmittance in the visible light range, and has excellent chemical stability. However, since the amount of deposits of In, a major component of ITO, is significantly smaller than the amount of deposits of Sn or zinc (Zn), the price of In is high, which is comparable to the price of silver (Ag). In addition, the price fluctuation of In is great, which is also problematic. Accordingly, studies of materials which can substitute for In are actively underway.
Recently, materials in which zinc oxide (ZnO) is doped with a group III cationic metal element, such as aluminum (Al), gallium (Ga), indium (In) or boron (B), or a halogen element, such as fluorine (F) were typically studied as substitute materials of ITO.
According to Korean Patent Application Publication No. 10-2008-0064269, the zinc oxide-based thin film can be deposited on a substrate by physical vapor deposition (PVD), and when sputtering is used in the PVD, a ZnO-based target is used as a target material.
In addition, according to Korean Patent Application Publication No. 10-2006-0125500, the zinc oxide-based thin film can be deposited on the substrate by chemical vapor deposition (CVD), in which diethyl zinc (DEZ), a DEZ octane solution or the like is used for a source material.
FIG. 1 is a view schematically depicting a plasma-enhanced chemical vapor deposition (PECVD) apparatus of the related art which deposits a zinc oxide-base thin film using diethyl zinc (DEZ) or dimethyl zinc (DMZ) as a source material.
FIG. 1 illustrates a PECVD apparatus which deposits undoped ZnO and F- and B-doped ZnO. The PECVD apparatus shown in FIG. 1 forms a reaction composition by combining DEZ or DMZ as a fugitive organic metal zinc compound, Ar or He as a carrier gas, CO2 as an oxidizer, and tetraethyl boron or nitrogen trifluoride (NF3) as a dopant, and blows the reaction composition into a deposition chamber 1, thereby depositing a zinc oxide-based thin film on a substrate 5.
Among the reference numerals which have not been described, 2 indicates an upper electrode, 3 indicates a lower electrode, 4 indicates a hole, 6 indicates an opening, 7 indicates a power source, 8, 9, 10, 11, 12 and 13 indicate lines, 14, 15, 16, 17, 18 and 19 indicate mass flow controllers (MFCs), and 20 indicates a thermostat.
FIG. 2 is a view schematically depicting a deposition chamber of the related art which deposits a zinc oxide-based thin film using a solution which was made by dissolving DEZ into an organic solvent as a source material.
A solution that was manufactured by dissolving DMZ or DEZ into an organic solvent (ether, ketone, ester, hydrocarbon or alcohol) is gasified. The gasified solution is supplied into a chemical vapor deposition (CVD) apparatus via a duct 24, and at the same time, an oxidizer gas (oxygen gas, ozone gas, nitrogen oxide gas or water vapor) is supplied into a deposition chamber via a duct 25.
Among the reference numerals which have not been described, 21 indicates a substrate, 22 indicates a susceptor, 23 indicates a heater, 26 indicates a rotary shaft, 27 indicates a reactant gas outlet, and 29 indicates a reaction chamber.
However, when DEZ or DMZ is used as in FIG. 1, there are problems in that the vapor pressure is too high, the danger of ignition is significant owing to high reactivity, it is not easy to control the composition of the thin film. In particular, there are disadvantages in that the deposition of the zinc oxide-based thin film using a precursor, such as DEZ or DMZ, must be carried out under low pressure, and that the atmospheric pressure chemical vapor deposition (APCVD) cannot be used.
In addition, although the method of using the precursor, such as DEZ or DMZ, by dissolving it into an organic solvent has an advantage of being capable of suppressing natural ignition, the disadvantage is that the yield is poor since the deposition rate is low owing to the low zinc content. Furthermore, since the solvent which has not volatized at a low temperature deposition increases the danger of ignition, this method must be used for only high temperature deposition, which is also disadvantageous.
The information disclosed in the Background of the Invention section is only for better understanding the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.
The information disclosed in the Background of the Invention section is only for better understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.